Gadd45beta in JNK Signaling, Apoptosis, and Cancer

描述（由申请人提供）：除了协调免疫和炎症反应外，NF-kappaB/Rel转录因子还控制细胞存活。这种抗凋亡功能对肿瘤发生、癌症化疗耐药和对抗tnf - r诱导的杀伤至关重要。通过功能筛选，我们发现Gadd4513/Myd 118是NF-kappaB抗TNFalpha凋亡保护活性的关键介质。Gadd45beta的细胞保护涉及JNK级联的抑制，这种抑制是NF-kappaB控制细胞死亡的核心。事实上，Gadd45a的表达依赖于NF-kappaB，纠正NF-kappaB缺失细胞的凋亡缺陷，对NF-kappaB依赖性存活至关重要。然而，NF-kappaB在肿瘤发生和抗癌治疗抵抗中的保护功能的基础仍然知之甚少。同样，凋亡过程中由Gadd45beta控制的步骤以及Gadd45beta抑制JNK信号传导的机制尚不清楚。这项建议有三个具体目标，将解决这些问题。在Aim 1中，通过结合体内和体外方法，我们将系统地检查Gadd45beta对fas诱导的BJAB细胞通路的影响，重点关注两个主要检查点：DISC和线粒体。我们还将评估靶向JNK级联与Gadd45beta控制fas诱导的杀伤的相关性。在Aim 2中，我们将确定Gadd45beta抑制JNK通路的机制，以及Gadd45beta特异性抑制JNK通路的基础。我们将首先评估新发现的Gadd45beta与JNK级联成分之间相互作用的意义。如有必要，我们将使用色谱方法鉴定Gadd451a中与JNK抑制和细胞保护相关的其他靶点。在Aim 3中，通过使用Ras转化和乳腺癌模型系统，我们将解决Gadd45beta的作用和NF-？B-dependent肿瘤发生。我们还将对原发性人类肿瘤中Gadd45beta的表达进行系统分析，重点关注那些依赖NF-kappaB生存的肿瘤。最后，我们研究了Gadd451a抗化疗药物凋亡活性对肿瘤细胞抗肿瘤治疗耐药的意义。这些研究的目的是确定Gadd45beta是否像NF-kappaB一样代表癌症治疗的靶标。

DESCRIPTION (provided by applicant): In addition to coordinating immune and inflammatory responses, NF-kappaB/Rel transcription factors control cell survival. This anti-apoptotic function is crucial to oncogenesis, cancer chemoresistance, and to antagonize TNF-R-induced killing. Using a functional screen, we have identified Gadd4513/Myd 118 as a pivotal mediator of the NF-kappaB protective activity against apoptosis by TNFalpha. Cytoprotection by Gadd45beta involves the inhibition of the JNK cascade, and this inhibition is central to the control of cell death by NF-kappaB. Indeed, Gadd45a expression depends on NF-kappaB, corrects the apoptotic defect of NF-kappaB null cells, and is essential to NF-kappaB-dependent survival. However, the bases for the NF-kappaB protective functions in oncogenesis and resistance to anti-cancer therapy remain poorly understood. Likewise, the step(s) controlled by Gadd45beta during apoptosis, and the mechanisms by which Gadd45beta inhibits JNK signaling are not known. This proposal has three Specific Aims, which will address these issues. In Aim 1, by combining an in vivo and an in vitro approach, we will systematically examine the impact of Gadd45beta on Fas-induced pathways in BJAB cells, focusing on two major checkpoints: the DISC and the mitochondria. We will also assess the relevance of the targeting of the JNK cascade to the control of Fas-induced killing by Gadd45beta. In Aim 2, we will determine the mechanisms by which Gadd45beta suppresses the JNK pathway and the bases for the specific inhibition of this pathway by Gadd45beta. We will begin by assessing the significance of newly discovered interactions between Gadd45beta and components of the JNK cascade. If necessary, by using chromatographic methods, we will identify the additional targets of Gadd451a that are relevant to JNK inhibition and cytoprotection. In Aim 3, by using the Ras transformation and breast cancer model systems, we will address the roles of Gadd45beta and the targeting of the JNK pathway in NF-?B-dependent tumorigenesis. We will also perform a systematic analysis of Gadd45beta expression in primary human tumors, focusing on those tumors that depend on NF-kappaB for their survival. Finally, we examine the significance of the Gadd451a anti-apoptotic activity against chemotherapy drugs to the resistance of tumor cells to anti-cancer treatment. The goal of these studies is to determine whether, like NF-kappaB, Gadd45beta represents a target for cancer therapy.